1. Field of the Invention
The present invention relates to photo-optical switching devices and more specifically to multiplane optical membrane switches for use in keyboard matrix arrays.
2. Description of the Prior Art
Prior art electrical membrane switching apparatus generally utilizes an electrically conductive coating on the opposite confronting surfaces of two slightly separated membranes. When the two membranes are pressed together electrical contact is made between the two conducting surfaces. If the conductive coatings are arranged in an array or matrix with one set of conductors at right angles to the other opposite set of conductors it is possible to form a keyboard with keys disposed at the intersections thereof.
Such keyboards suffer from certain deficiences not the least of which is the fact that they radiate electromagnetic energy and are susceptible to electromagnetic interference (EMI). By employing optically conducting membranes the EMI problems are eliminated, in as much as there are no electrical contacts to be made.